NOD2 is a proposed nucleotide-binding protein involved in the innate immune recognition of the bacterial cell wall components, muramyl dipeptide. NOD2 is implicated in conditions of chronic inflammation within the human gastrointestinal tract. These inflammatory conditions are now widely recognized as predisposing factors in the development of various malignancies. Mutations in the gene encoding this NOD2 have been linked to susceptibility to Crohn's Disease, one of two primary forms of Inflammatory Bowel Disease. Epithelial expression of NOD2 is also upregulated by Helicobacter pylori exposure. Additionally, a Crohn's disease associated mutation in NOD2 was recently linked to increased incidence of the Helicobacter pylori-induced lymphoma (MALT). The mechanisms underlying the activation of NOD2 during physiologic responses to bacteria or in the setting of disease-associated mutations remain to be determined. Though, nucleotide binding and hydrolysis are central to the regulation of many NOD2 related proteins, these properties have not been studied in NOD2. Various nucleotide analogs with specificity for disease associated molecular targets are used to combat many human illnesses. We propose to: 1) characterize the nucleotide-binding properties of NOD2 proteins, 2) define the role nucleotide binding by this protein contributes to its function, and 3) establish whether this process is altered by disease- associated mutations of NOD2. We believe these studies will shed light on both the mechanism of Crohn's Disease pathogenesis and chronic inflammation within the gut mucosa, which is associated with carcinogenesis. These studies are important to further our understanding of the regulation of NOD2 activity. They will answer fundamental questions regarding the molecular mechanisms underlying diseases caused by NOD2 mutations. They will also set the stage for future investigations into the details of NOD2 function. PUBLIC HEALTH RELEVANCE: NOD2 is a nucleotide binding protein involved in initiating and maintaining inflammation within the gastrointestinal system. Patients with chronic inflammation are at higher risk for numerous conditions including the development of cancers. Understanding the nucleotide binding properties of NOD2 may ultimately lead to the development of pharmacologic agents that can modify signaling by NOD2, which would have clinical application in intestinal inflammatory conditions.